Variations of the Timing of Deflections in the His Bundle Recordings

Clinical and experimental studies were performed to examine the meaning and implication of the "His bundle spike" recorded with the current techniques. Tracings obtained with various locations of electrodes along the A-V conducting system revealed that the more ventricularly the sensing electrode(s) was (were) introduced, the shorter the interval between the "His bundle spike" and the onset of ventricular deflections (spike-Q interval) on the electrogram. The His bundle and bundle branch potentials should be understood not as the discrete phenomena but as the local manifestations of the suc-cessive depolarization of the A-V conducting system. The His potential observed in a bipolar lead with 2 catheter electrodes was occasionally not seen in a unipolar lead with one of the 2 electrodes, therefore, the measurement of the intervals of the deflections would be of clearer meaning with unipolar lead which is more suitable for detailed study of the A-V conduction. Calculated condution velocity in human His bundle approximated to 1.25M/sec.